devcontainer setup and add a test

[MatthewCaseres]

Curious what you think about this -

• adds poetry which should help with publishing/managing environment. This is done by using a "Python devcontainer", and then installing poetry with a "postCreateCommand"
• adds pytest, I did a single test but this should be expanded.
• adds CI/CD

You should be able to open in codespaces and then once the postCreate.sh script runs, run pytest when poetry shell is active. The container also includes https://github.com/nektos/act so you can locally test GitHub workflows quickly and without committing changes.

[MatthewCaseres]

• not super sure which python versions should be supported. I just test on I think 3.9 but we can test on all versions that should be supported.
  • removed dependency for "six" which seems like a python2 back compatibility thing.